This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Genetic evidence indicates that KIR and HLA class I polymorphisms play an important role in determining the rate of disease progression in HIV-1 infected individuals. However, the immunological mechanisms underlying these observations are poorly understood. We recently identified Mamu-A1*00201 (Mamu-A*02), a common MHC class I molecule in the rhesus macaque, as a ligand for Mamu-KIR3DL05. Using KIR- and MHC class I-defined animals, experiments can now be designed to examine the role of this KIR-MHC class I interaction in the regulation of NK cell responses to SIV infection.